In optics, coherence is a measurement of how closely two signals compare, or correlate, to each other or how closely a signal compares to itself. Prior art methods of measuring coherence between two signals or of one signal involved frequency analysis and calculations of the power spectral densities. There is, however, a need for a device for and method of signal coherence measurement that is better suited to digital signal processing techniques that does not require spectral estimation.
(U) U.S. Pat. No. 6,580,492, entitled “RETICLE SYSTEM FOR MEASUREMENT OF EFFECTIVE COHERENCE FACTORS,” discloses an optical method of measuring coherence. U.S. Pat. No. 6,580,492 is hereby incorporated by reference into the specification of the present invention.
(U) U.S. Pat. No. 6,992,779, entitled “INTERFEROMETER APPARATUS FOR BOTH LOW AND HIGH COHERENCE MEASUREMENT AND METHOD THEREOF,” discloses an optical method of measuring coherence. U.S. Pat. No. 6,992,779 is hereby incorporated by reference into the specification of the present invention.